The present invention generally pertains to biocompatible implants for localized delivery of pharmaceutically active agents to body tissue. More particularly, but not by way of limitation, the present invention pertains to biocompatible implants for localized delivery of pharmaceutically active agents to the posterior segment of the eye.
Several diseases and conditions of the posterior segment of the eye threaten vision. Age related macular degeneration (ARMD), choroidal neovascularization (CNV), retinopathies (i.e. diabetic retinopathy, vitreoretinopathy), retinitis (i.e. cytomegalovirus (CMV) retinitis), uveitis, macular edema, and glaucoma are several examples.
Age related macular degeneration (ARMD) is the leading cause of blindness in the elderly. ARMD attacks the center of vision and blurs it, making reading, driving, and other detailed tasks difficult or impossible. About 200,000 new cases of ARMD occur each year in the United States alone. Current estimates reveal that approximately forty percent of the population over age 75, and approximately twenty percent of the population over age 60, suffer from some degree of macular degeneration. xe2x80x9cWetxe2x80x9d ARMD is the type of ARMD that most often causes blindness. In wet ARMD, newly formed choroidal blood vessels (choroidal neovascularization (CNV)) leak fluid and cause progressive damage to the retina.
In the particular case of CNV in ARMD, two main methods of treatment are currently being developed, (a) photocoagulation and (b) the use of angiogenesis inhibitors. However, photocoagulation can be harmful to the retina and is impractical when the CNV is near the fovea. Furthermore, photocoagulation often results in recurrent CNV over time. Oral or parenteral (non-ocular) administration of anti-angiogenic compounds is also being tested as a systemic treatment for ARMD. However, due to drug-specific metabolic restrictions, systemic administration usually provides sub-therapeutic drug levels to the eye. Therefore, to achieve effective intraocular drug concentrations, either an unacceptably high dose or repetitive conventional doses are required. Periocular injections of these compounds often result in the drug being quickly washed out and depleted from the eye, via periocular vasculature and soft tissue, into the general circulation. Repetitive intraocular injections may result in severe, often blinding, complications such as retinal detachment and endophthalmitis.
In order to prevent complications related to the above-described treatments and to provide better ocular treatment, researchers have suggested various implants aimed at localized delivery of anti-angiogenic compounds to the eye. U.S. Pat. No. 5,824,072 to Wong discloses a non-biodegradable polymeric implant with a pharmaceutically active agent disposed therein. The pharmaceutically active agent diffuses through the polymer body of the implant into the target tissue. The pharmaceutically active agent may include drugs for the treatment of macular degeneration and diabetic retinopathy. The implant is placed substantially within the tear fluid upon the outer surface of the eye over an avascular region, and may be anchored in the conjunctiva or sclera; episclerally or intrasclerally over an avascular region; substantially within the suprachoroidial space over an avascular region such as the pars plana or a surgically induced avascular region; or in direct communication with the vitreous.
U.S. Pat. No. 5,476,511 to Gwon et al. discloses a polymer implant for placement under the conjunctiva of the eye. The implant may be used to deliver neovascular inhibitors for the treatment of ARMD and drugs for the treatment of retinopathies, retinitis, and CMV retinitis. The pharmaceutically active agent diffuses through the polymer body of the implant.
U.S. Pat. No. 5,773,019 to Ashton et al. discloses a non-bioerodable polymer implant for delivery of certain drugs including angiostatic steroids and drugs such as cyclosporine for the treatment of uveitis. Once again, the pharmaceutically active agent diffuses through the polymer body of the implant.
All of the above-described implants require careful design and manufacture to permit controlled diffusion of the pharmaceutically active agent through a polymer body (matrix devices) or polymer membrane (reservoir devices) to the desired site of therapy. Drug release from these devices depends on the porosity and diffusion characteristics of the matrix or membrane, respectively. These parameters must be tailored for each drug moiety to be used with these devices. Consequently, these requirements generally increase the complexity and cost of such implants.
U.S. Pat. No. 5,824,073 to Peyman discloses an indentor for positioning in the eye. The indentor has a raised portion that is used to indent or apply pressure to the sclera over the macular area of the eye. This patent discloses that such pressure decreases choroidal congestion and blood flow through the subretinal neovascular membrane, which, in turn, decreases bleeding and subretinal fluid accumulation.
Therefore, a need exists in the biocompatible implant field for a surgically implantable drug delivery device capable of safe, effective, rate-controlled, localized delivery of a wide variety of pharmaceutically active agents to any body tissue. The surgical procedure for implanting such a device should be safe, simple, quick, and capable of being performed in an outpatient setting. Ideally, such a device should be easy and economical to manufacture. Furthermore, because of its versatility and capability to deliver a wide variety of pharmaceutically active agents, such an implant should be capable of use in clinical studies to deliver various agents that create a specific physical condition in a patient or animal subject. In the particular field of ophthalmic drug delivery, such an implantable drug delivery device is especially needed for localized delivery of pharmaceutically active agents to the posterior segment of the eye to combat ARMD, CNV, retinopathies, retinitis, uveitis, macular edema, and glaucoma.
One aspect of the present invention comprises a drug delivery device including a body having an internal surface for placement proximate a target tissue and a well having an opening to the internal surface. An inner core comprising a pharmaceutically active agent is disposed in the well.
In another aspect, the present invention comprises a method of delivering a pharmaceutically active agent to a target tissue within a body. A drug delivery device is provided. The drug delivery device includes a body having an internal surface and a well having an opening to the internal surface, and an inner core disposed in the well comprising a pharmaceutically active agent. The device is disposed within the body so that the pharmaceutically active agent is in communication with the target tissue through the opening.
In a further aspect, the present invention comprises an ophthalmic drug delivery device including a body having a scleral surface for placement proximate a sclera and a well or cavity having an opening to the scleral surface. An inner core comprising a pharmaceutically active agent is disposed in the well.
In a further aspect, the present invention comprises a method of delivering a pharmaceutically active agent to an eye having a sclera. A drug delivery device is provided. The drug delivery device includes a body having a scleral surface and a well having an opening to the scleral surface, and an inner core disposed in the well comprising a pharmaceutically active agent. The device is disposed within the eye so that the pharmaceutically active agent is in communication with the sclera through the opening.
In a further aspect, the present invention comprises a method of delivering a pharmaceutically active agent to an eye having a sclera, a Tenon""s capsule, and a macula. A drug delivery device comprising a body having a pharmaceutically active agent disposed therein is provided. The device is disposed on an outer surface of the sclera, below the Tenon""s capsule, and proximate the macula.